In this lesson video, we are going to discuss the mirror modifier which we can use to make an object becomes symmetrical. This is important as a lot of 3d models that we want to create are symmetrical, such as cars, characters, furniture, etc. to make an object symmetrical, we can actually use two different methods. First is by using the symmetrized mesh operation, and second by using the mirror modifier. Previously, we already learned how to use the symmetrize mesh operation. So now the only method we haven't discussed yet is the mirror modifier.

Mirror modifier. As the name implies, we will create a mirror version of the object. For example, here we have a monkey head model. To add a mirror modifier, make sure the object is selected. Then go to the modifier panel in the Properties editor, add modifier and then choose mirror here at a glance It seems that nothing has happened to the object. This is because the original object is already symmetrical.

But if we go to the edit mode, and move all of the mesh elements around, as we can see, we actually have two measures here. The first one is the original mesh that we can edit, and the second one is the mesh generated by the mirror modifier. By default, the origin of the object is used as the center or as the mirror plane location, ie the modifier panel, we can see that the mirror modifier comes with several options. The X, Y, Z axis checkboxes here at the left, determine the direction of where the mirror will happen. By default Blender will use the x axis. So the direction of the reflection is this way.

If we choose y, this is what happens. If we move the mesh around. We can see the mirror happens on y axis. If we choose z, it will be like this. Okay, we can turn on multiple axes at the same time if you want to, so we can get this kind of result. I am sure we get the idea here.

Now, most of the time, we don't want these measures to overlaps like this. So the idea of workflow when using the mirror modifier is you need to cut the object half exactly at the origin location, and then delete the faces or the vertices at the side we want to ignore. In a previous version, you have to do this manually. But since Blender 2.8. Now you can use this bisect options to remove the half part automatically, just like the mirror axis, you can turn on or off bisect for each of the axes. I think to make this more clear, let's just focus on the z axis for now.

Turn off the other checkboxes and just use the z axis for now. If we go back out to the object mode, we can see two mouse one at the top and one at The bottom, if we turn on the Z bisect checkbox, the mouse are now gone. So bisect is like cutting the model with a knife and just remove the other half that is penetrating the mirror plane. Now what if we actually want to see the mouth and not the eyes? Well, this was this flip options do. If we click on this z flip checkbox, we are mirroring the bottom to top instead of the top to bottom.

Let me turn off these z options and just use the x axis and x by sec here, the mirror object here we let you ignore the origin and use another object as the mirror plane. For example, if you press shift a and then create an empty object, I prefer these arrows type as it displays the access. If you don't know what empty object is, basically it is just a dummy object that will not get rendered when we do the final rendering. So it does not contain any mesh data but because The objects do have transformation data like the location, rotation and scale. We can use empty objects for overriding or controlling transformation value such as the case with this mirror modifier. To select this empty object, we can click here, Blender will list all of the objects in the scene that can be used to override the mirror plane location.

We can select the empty object here, or you can also use this eyedropper icon here, and then click on the empty object to pick it. After it is assigned. We can see the name of the empty object here. If we move the empty object around, we can see we are removing the mirror plane of the mirror modifier. If you don't need the empty object anymore, to release it, you can click this X button here. The vertex group option here will mirror the vertex group assignment that you already made in the model.

Now we We haven't discussed about vertex group yet, so we need to skip this for now. Next is the clipping option. The clipping option is probably the most helpful feature when it comes to the modeling process. Basically, it will constrain the position of the vertices in our object so they won't bypass or cross the mirror plane to show you what I mean. Go to the vertex mode, and choose this vertex and then move this to a board this position crossing the mirror plane. We can see with the clipping option turned off, we can freely move sub objects across the mirror plane.

Let me undo this first. Now let's turn on the clipping option. Notice with the clipping option turned on, if we try to move this vertex to the left side again, it cannot bypass the clipping plane no matter how hard we try. And this is nice so we can easily and precisely place vertices on the mirror plane without worries. The merge option here, we will merge the adjacent vertices at the mirror plane. Mostly, you always want to turn this option on.

Otherwise, if you turn it off, when you apply the modifier, you will have double vertices along the center area where the mirror happens. The merge limit values here only works if we have the merge option up here turned on. Essentially, this value determines how close the vertices should be for the merge operation to work. The last one is the textures options. Basically, these options allow you to flip the UV map when you perform mirroring. That is if the object already has a UV map.

Now if you don't know what you feel map yet, don't worry. We will have a dedicated section about texturing and UV mapping in this score series. For now, we just have to skip this part. We will revisit this again when we discuss UV mapping.